I'd like to give a +1 for Beekeeb as a vendor. Leo there is a rockstar with incredible support. They provide kits with everything in them so you can assemble them like Legos, or presoldered and assembled boards too. Beyond that, Beekeeb invests in open source, often releasing new designs but also publishing variations of boards and cases and firmware for all of us to use.

A good place to start is our wiki, you'll find there a small list of some popular keyboards as well as links to other databases of keyboards what hopefully will help you. some obvious ones: Corne (crkbd), Kyria, Iris, Lily58, Sofle, Sweep.

If you search, the open-source ones linked generally are being sold as kits in a few places, so have a look around. you can see a list of vendors in our wiki too, it may not be exhaustive but it's pretty comprehensive.

I'm an absolute beginner, and I went with Beekeeb's Piantor keyboard. I couldn't be happier.

The MBK Legend keycaps have homing versions for Colemak and Dvorak in standard kit if you go that route. They're great keycaps

Depending on what region you're in, there's probably gonna be some folks selling cool ergomech kits. I'm personally in the EU, can recommend keeb.supply, Keycapsss, 42keebs, splitkb.com, Keygem.

I'm probably forgetting some, and these are only the EU-based ones. Maybe someone else could recommend vendors in other regions :)